This section provides background information related to the present disclosure which is not necessarily prior art.
In the internal combustion engines in use today, it is common to use a portion of the exhaust gasses to improve the engine performance or the emissions of the combustion. A typical benefit of the use of the exhaust gas recirculation (EGR) is the reduction of the peak combustion temperature in order to avoid the creation of pollutants like NOx or the reduction of the required amount of throttling in gasoline engines. Typically, the recirculation is obtained by an external piping which brings a portion of the exhaust gasses back into the intake manifold.
In recent years, an improved internal exhaust gas recirculation (internal EGR) technique has been used in order to minimize the waste of energy (waste of heat through the piping loop, waste of flow dynamic losses along the piping) of such a system bringing further benefits like the more stable combustion in cold conditions, the reduction of pollutants or an improvement of fuel efficiency. The internal EGR technique includes the opening of the exhaust gas valve during the intake stroke phase creating a so-called rebreathing lift. The control of the amount of internal EGR is obtained by applying a higher or lower lift of the exhaust valve during the intake stroke of the cylinder where the differential pressure between the exhaust manifold and the combustion chamber is in favor of filling the combustion chamber itself with exhaust gasses.
Controlling the amount of internal EGR only with the usage of a higher or lower re-breathing lift brings to an edge where a small variation of such a lift corresponds to a huge variation of the gas recirculated. Such a situation limits the usage of the internal EGR technique to a restricted area of the engine map.